FH&W takes inspiration from the earlier editions of D&D(most of it is based on AD&D) and blends oldschool mood with more modern design sensibilities(picking some of the better changes from 3E to include) while adding a hefty helping of unique stuff.
The conveniences you have come to expect from more progressive Retroclones, like a unified experience table, Base Attack Bonus instead of THAC0, or a streamlined saving throw system(a single target number, starting high and going down with experience, combined with bonuses/penalties of the targeted attribute) are all there, but what really sets it apart are the changes/additions that go beyond tweaking the base mechanics(the Friar, for example, eschews traditional spell-slot based casting in favor of a prayer system and is much closer to what one would imagine upon hearing the word "priest", than the much more militant and overtly magical Cleric).
There is an abundance of choice, whether you are looking at races, classes, or spells; easily letting you cover different themes(from traditionaly fantasy over steampunk, to post-apocalypse, science fantasy...). You don't just get thrown headfirst into a single list of classes ranging from Fighter to Sky-Lord(basically an ace pilot) though, instead the game presents most themed content in its own section(for example the chapter discussing religions lists various specialty priest types, agents of higher forces and sample gods). As such, it doesn't bloat the list of core classes(which covers the classic staples) while offering extra content for whatever theme you want to focus on or feature more prominently.
There is no baked-in setting, but the wide variety and sheer amount of content makes it easy to plug in an existing one or make up your own without having to do much work as far as having to write up appropriate classes etc. goes. Take note that there are also no monsters or magic items included, so this technically isn't a stand alone book.
However, adapting content from AD&D should be a breeze(in fact, you can probably use most stuff as is, without any changes) and the author is already working on a monster book.
If you are even remotely interested in OSR gaming, you don't want to pass this one up.
[5 of 5 Stars!]